Non-metallic load center with improved bus bar construction

ABSTRACT

A non-metallic load center comprises an insulative, molded plastic enclosure consisting of a housing having integrally formed back and sidewalls and a separable cover. An elongated bus bar having first and second strip portions interconnected by spaced L-shaped ribs is secured adjacent its ends to integrally formed mounting posts. Bus bar contacts extend into each gap between adjacent ribs to facilitate electrical contacting engagement with individual circuit breakers, while the ribs afford lateral stability to the individual circuit breaker installations. Integrally formed pedestals afford bus bar support intermediate its ends and also serve to support and locate a connector lug carried by the bus bar.

1 Apr. 2, 1974 NON-METALLIC LOAD CENTER WITH IMPROVED BUS BARCONSTRUCTION [75] Inventors: John Alfred Morby, Bristol; James EdwardMcGann, Forestville, both of Conn.

[73] Assignee: General Electric Company, New J York, N.Y.

[22] Filed: June 14, 1973 [21] Appl. No; 369,867

3,743,892 7/1973 Fritz 317/119 Primary Examiner-James R Scott AssistantExaminerGerald P. Tolin Attorney, Agent, or Firm-Robert A. Cahill;Philip L. Schlamp; Frank L. Neuhauser [57 ABSTRACT A non-metallic loadcenter comprises an insulative, molded plastic enclosure consisting of ahousing having integrally formed back and sidewalls and a separablecover. An elongated bus bar having first and second strip portionsinterconnected by spaced L-shaped ribs is secured adjacent its ends tointegrally formed mounting posts. Bus bar contacts extend into each gapbetween adjacent ribs to facilitate electrical contacting engagementwith individual circuit breakers, while the ribs afford lateralstability to the individual circuit breaker installations. integrallyformed pedestals afford bus bar support intermediate its ends and alsoserve to support and locate a connector lug carried by the bus bar.

8 Claims, 5 Drawing Figures ATENIEDAPR 21914 1801875 SHEET 2 [IF 3MENTED APR 2 I974 SHEEI 3 OF 3 W In.

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NON-METALLIC LOAD CENTER WITH IMPROVED BUS BAR CONSTRUCTION BACKGROUNDOF 'I'HF, INVENTION Heretofore, enclosures for electrical equipment,such as circuit breaker panelboards or load centers, have invariablybeen metallic. These metallic enclosures are manufactured in massproduction from metal sheets in a succession of operations, includingcutting, blanking, forming and welding, to create a box-like housing,which must then be painted. The enclosure covers are similarly producedin a succession of operations. A number of components, includingcomponent mounting and supporting elements, must then be assembled inthe box-like housing. Since the metallic enclosure is electricallyconductive, insulators must be incorporated into the mounting of thevarious bus bars to the enclosure.

Recently, a non-metallic, molded plastic electrical equipment enclosurein the form of a circuit breaker panelboard or load center has beenintroduced in the market and offers numerous advantages over itsmetallic counterpart. The complete box-like housing can be created in asingle molding operation, as can the cover. Painting is unnecessary, andthe plastic can be readily tinted and the mold designed to create asurface finish which is esthetically pleasing. Moreover, mounting andsupporting elements may be integrally formed with the enclosure, thussimplifying assembly. In this context, the assembly of separateinsulating members is obviated since the enclosure itself is anexcellent insulator. As a consequence, a molded plastic enclosure ischeaper to manufacture in mass production than a comparable metallicenclosure. Moreover, electricians have found the molded plasticenclosure more convenient to install and wire.

It is accordingly an object of the present invent to provide anon-metallic, molded plastic enclosure of the above characterparticularly adapted as a circuit breaker panelboard or load center.

Still another object of the invention is to provide a molded plasticcircuit breaker load center of the above character, having an improvedmain bus bar configuration.

A further-object is to provide a non-metallic load center of the abovecharacter incorporating improved provisions for mounting and supportingthe main'bus bar.

Other objects of the invention will in part be obvious and in partappear hereinafter.

SUMMARY OF THE INVENTION In accordance with the invention, there isprovided a non-metallic, molded plastic enclosure for electricalequipment, such as a panelboard or load center for circuit breakers,having integrally formed back and side'- wallsin the configuration of'abox-like housing.A separable molded plastic cover for the housingcompletes the enclosure. Integrally formed with the housing are therequisite mounting and supporting provisions for the various electricalcomponents, including a pair of spaced mounting posts on which the endsof a main bus bar are secured. The main bus bar is uniquely structuredand configured to accept electrical contacting engagement withindividual circuit breakers, while affording lateral stabilization to'the individual circuit breaker installations. Moreover, the housing isstructured to lend mechanical support to the main bus bar, particularlyduring circuit breaker installation and wiring at the site ofutilization.

More specifically, the main bus bar includes first and second elongated,planar conductive portions arranged at right angles and interconnectedby a series of spaced, L-shaped ribs. The first portion is securedadjacent its ends to the mounting posts in parallel, spaced relation tothe housing backwall. The free edge of the second portion rests againstthe housing backwall and is formed having a blade contact extending fromits opposite edge at each location between adjacent ribs. The spacingbetween adjacent ribs closely approximates the standard width of acircuit breaker at its contact location. Consequently, upon installationof a circuit breaker in electrically contacting engagement with eachmain bus bar contact, the forces of installation on the main bus bar areresisted by the housing backwalls engagement with the free edge of thebus bar second portion. Moreover, the ribs lend lateral stability to thecircuit breaker installations.

It will be appreicated that, since the housing itself is of anelectrically insulating plastic material, separate electricallyinsulating members interposed between the engaging surfaces of the mainbus bar and the housing are unnecessary.

In an alternate embodiment of the invention, the main bus bar isstructured to accept a lug connector which is located and supported,particularly during the connection of a main line thereto, by a pedestalintegrally formed with the housing.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of anon-metallic enclosure for electrical equipment constructed inaccordance with the invention'to include a molded plastic, box-likehousing and a separable molded plastic cover;

FIG. 2 is a plan view from the open side of the housing of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a perspective view of the main lug connector and a portion ofthe main bus bar seen in FIGS. 2 and 3;'and

FIG. 5 is a perspective view of a main bus bar constructed in accordancewith an alternate embodiment of the invention.

Like reference numerals refer to corresponding parts throughout theseveral views of the drawings.

DETAILED DESCRIPTION A non-metallic enclosure for electrical equipment,constructed according to the invention, is seen in FIG. 1 to include amolded plastic, box-shaped housing, generally indicated at 10, and aseparable cover, generally indicated at 12. The housing and cover areformed of a suitable plastic, preferably a thermoplastic material, suchas a phenylene-oxide thermoplastic marketed by General Electric underthe trademark NORYL. The housing 10, also seen in FIG. 2, comprises abackwall l4 and four integral sidewalls l6, l7, l8 and 19. Cover 12comprises a front wall 21 and shallow sidewalls 22,

all formed in a single molding operation. The housing sidewallsterminate in a perimetrical lip 24 surrounding the open front of thehousing 10, which is telescopically received within cover sidewalls 22when cover 12 is mounted in place. Referring to FIG. 1, the upperhorizontal portion of lip 24 carries a pair of molded, pyramidal-shapedhooks 26 which are received in apertures 28 molded in the upper coversidewall 22, and the cover is pivoted into closure relation with thehousing. The cover is held in place by a screw 30 passing throughaperture 31 and threaded through a hole 31a in an equipment ground busbar 44.

The front wall 21 of cover 12 is molded to provide a row of knockouts 33which are removed to provide apertures accommodating the protrusion,with the cover in place, of the digitally operative portion of circuitbreakers installed in housing 10, one being shown so installed at 34 inFIG. 1. The back and sidewalls of housing are molded to provide a seriesof conveniently located knockouts 36 which are selectively removed toaccommodate the introduction of cable during wiring installation of theload center. Tabs 38 integrally molded with housing 10 facilitate thephysical mounting of the load center at the site of wiring instal-.

lation.

Turning to FIG. 2, assembled in housing 10 are three bus bars, namely, amain bus bar, generally indicated at 40, a neutral bus bar 42 and anequipment ground bus bar 44. Neutral bus 42 is captured at one end in amolded keyway 46 integrally formed with housing sidewall 18 and islocked in place by a screw 48 passing through a hole (not shown) in itsother end and threaded into a mounting post 50, also integrally formedwith housing 10. Neutral bus 42 carries a connector 52 facilitating theclamping of the bare ends of neutral wires (not shown) in electricalcontacting engagement therewith. Equipment ground bus 44 is similarlymounted at its ends by a molded keyway 46, integral with housingsidewall 17, and mounting post 32 by a screw 50. A connector 52similarly facilitates clamping the bare ends of ground wires inelectrical contacting engagement with bus 44.

The main bus bar 40, as seen in FIGS. 2 and 3, includes an elongatedplanar conductive strip 60 mounted adjacent its end in parallel spacedrelationship to housing backwall 14 by grally molded with the housingbackwall. Strip 60 is clamped in place by the heads of screws 62threaded into mounting posts 64. A notch 61 in strip 60 providesclearance with respect to a molded mounting post 63 used in mounting analternative cover form. A second planar, conductive strip 66, extendingin the same direction as strip 60 but arranged at a right angle thereto,is interconnected to strip 60 by a series of spaced, L-

' shaped ribs 68. The bottom edge of strip 66 rests on housing backwall14, as best seen in FIG. 3. A blade contact 70 extends upwardly from theupper edge of strip 66 into the gap between each adjacent pair of ribs68. The spacing betweenadjacent ribs corresponds to the standard widthof the circuit breaker 34 in the area of its contacts, as seen inphantom in-FIG. 2, such that the ribs afford lateral stability to theindividual circuit breakers when installed in electrical contactingengagement with the respective blade contacts 70. That is, the ribs 68bear against the circuit breaker case sidewalls to resist any lateralsway of-the circuit breakers. Moreover,-the support afforded by thehousing backwall, against which the bottom edge of the strip 66- rests,is effective particularly during circuit breaker installation, to resistdamage to the main bus 40. In addition,

mounting posts 64, intea pedestal 72, integrally formed with housing 10,af-

' 14. The free edge of this flange is interconnected back to thebackwall by a series of spaced tabs 82 to form openings 84 arrayed inconfronting relation to main bus 40. As seen in FIGS. 1 and 2, thebreaker case is formed with a pair of spaced hooks 85 which are insertedin adjacent openings 84 to straddle the intervening tab 82. The circuitbreaker 34 is then pivoted into electrical contacting engagement withthe aligned one of the contacts 70.

The main bus 40 seen in FIGS. 2 and 3, is structured to accept a lugconnector, carried by strip 60 and gen erally indicated at 86. Strip 66is shorter in length than strip 60, such that main bus 40 accepts threecircuit breakers in the illustrated embodiment; the lug connector beingcarried by the portion of strip 60 extending beyond strip 66. Lugconnector 86, as best seen in FIG. 4, is formed from a conductive stripinto a rectangular configuration having a top wall 860, sidewalls 86band 860, and bottom wall 86d. The connector sidewalls are formed withaligned slots 86 through which the end of strip 66 extends in mountingconnector lug 86 to bus bar 40. The free end of bottom wall 86d isformed with a tongue 88 (FIGS. 3 and 4) which extends through the lowerportion of slot 87 in connector lug sidewall 86b. As seen in FIG. 2,strip 60 is provided with a shoulder 60a which engages sidewall 86b toestablish the leftmost position of connector lug 86 on bus bar 40. Then,as seen in FIG. 3, a supporting pedestal 90 is integrally formed withhousing backwall 14 at a location to provide a seat for connector lug 86when main bus bar 40 is factory assembled in housing 10. To establishthe right-most portion of the connector lug on the main bus bar,pedestal 90 is relieved, as indicated at 91, to accommodate the lowerextension of sidewall 86b beyond bottom wall 86d. A set screw 92 isadvanced through a threaded hole in top wall 86a into the open interiorof the connector lug to clamp the inserted bare end of the lineconductor (not shown) into electrically contacting engagement with themain bus bar. The forces exerted incident to this wiring operation areresisted'by pedestal 90 to prevent distortion and damage to the main busbar.

The alternative main bus configuration, seen in FIG. 5 and generallyindicated at 93, accommodates the application of power to the main busvia a main circuit breaker, rather than a lug connector as in the firstem bodiment. As a consequence, main bus strips 94 and 96' arecoextensive in length to accommodate, in the illustrated embodiment,five'circuit breakers in the spaces between interconnecting ribs 68.Main bus 93 isassembled in housing 10 in the same manner as main bus 40with screws 62 passing through hole 97 and slot 98 located adjacent theends of strip 94; the screws threading into mounting posts 64. Notch 61in strip 94 affords clearance from mounting-post 63. While pedestal 90terminates in spaced relation to strip 94, pedestal 72 providesmid-length support for bus bar- 93. As in the case of bus bar 40, thebottom edge of strip 96 rests on the backwall 14 of housing to supportbus bar 93 during circuit breaker installation.

It will be appreciated that the advantages afforded by the main bus barconstructions disclosed herein are also obtained when assembled inmetallic electrical equipment enclosures. All that is required is theinclusion of electrically insulating elements in the mounting provisionsfor bus bars 40 or 93 to provide isolation from the metallic enclosure.

It will thus be seen that the objectives set forth above, among thosemade apparent from the preceding description, are efficiently attainedand, since certain changes may be made in the above constructionswithout departing from the scope of the invention, it is intended thatall matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

Having described our invention, what we claim as new and desire tosecure by Letters Patent is:

1. A circuit breaker panelboard, comprising, in combination:

A. a molded, electrically insulative housing including a backwall andintegrally formed, upstanding sidewalls;

B. a cover for said housing;

C. a pair of spaced mounting posts integrally formed with one of saidwalls;

D. a bus bar including l. a first elongated strip portion having meansadjacent each end facilitating securing said first strip portion to saidmounting posts in generally parallel, spaced relation to said backwall,

2. a second elongated strip portion,

3. a series of L-shaped ribs inter-connecting said first and secondstrip portions, and

4. an integral blade contact carried by said second strip portion andprojecting into each gap between adjacent ribs,

5. the spacing between adjacent ribs corresponding to the width of acircuit breaker case, whereby said ribs act to laterally stabilize theindividual circuit breakers when installed in electrically contactedengagement with respective ones of said blade contacts; and

E. common circuit breaker retaining means integrally formed with saidbackwall in parallel spaced relation to said bus bar.

2. The panelboard defined in claim 1, wherein an edge of said secondstrip portion rests on and is supported by said backwall during theinstallation of circuit breakers.

3. A panelboard defined in claim 1, wherein said first and second stripportions are coextensive in length.

4. The panelboard defined in claim 1, which further includes a pedestalintegrally formed with one of said walls and located to providemid-length support to said first strip portion.

5. The panelboard defined in claim 1, wherein said second strip portionterminates short of one end of said first strip portion, said panelboardfurther including an electrical connector mounted by said first stripportion at a location beyond the termination of said first stripportion.

6. The panelboard defined in claim 5, wherein said connector is formedhaving aligned slots accommodating the extension therethrough of thefirst strip portion, said panelboard further including a pedestalintegrally formed with said backwall and located to provide support forsaid connector.

7. The panelboard defined in claim 6, wherein said first strip portioncarries an abutment for engagement with said connector to establish itsapproximate position on said first strip portion in one direction, andsaid pedestal is formed having means for engaging means carried by saidconnector to locate its approximate position on said first strip portionin the opposite direction.

8. A circuit breaker panelboard, comprising, in combination:

A. a housing including a backwall and upstanding sidewalls; B. a coverfor said housing; C. a pair of spaced mounting means supported in saidhousing; D. a bus bar including:

1. a first elongated strip portion having means adjacent each endfacilitating securing said first strip portion to said mounting means ingenerally parallel, spaced relation to said backwall,

2. a second elongated strip portion,

3. a series of L-shaped ribs inter-connecting said first and secondstrip portions, and

4, an integral blade contact carried by said second strip portion andprojecting into each gap between adjacent ribs,

5. the spacing between adjacent ribs corresponding to the'width of acircuit breaker case, whereby said. ribs act to laterally stabilize theindividual circuit breakers when installed in electrically contactedengagement with respective ones of said blade contacts; and

E. common circuit breaker retaining means positioned in said housing inparallel spaced relation to said bus bar.

1. A circuit breaker panelboard, comprising, in combination: A. amolded, electrically insulative housing including a backwall andintegrally formed, upstanding sidewalls; B. a cover for said housing; C.a pair of spaced Mounting posts integrally formed with one of saidwalls; D. a bus bar including
 1. a first elongated strip portion havingmeans adjacent each end facilitating securing said first strip portionto said mounting posts in generally parallel, spaced relation to saidbackwall,
 2. a second elongated strip portion,
 3. a series of L-shapedribs inter-connecting said first and second strip portions, and
 4. anintegral blade contact carried by said second strip portion andprojecting into each gap between adjacent ribs,
 5. the spacing betweenadjacent ribs corresponding to the width of a circuit breaker case,whereby said ribs act to laterally stabilize the individual circuitbreakers when installed in electrically contacted engagement withrespective ones of said blade contacts; and E. common circuit breakerretaining means integrally formed with said backwall in parallel spacedrelation to said bus bar.
 2. a second elongated strip portion,
 2. asecond elongated strip portion,
 2. The panelboard defined in claim 1,wherein an edge of said second strip portion rests on and is supportedby said backwall during the installation of circuit breakers.
 3. Apanelboard defined in claim 1, wherein said first and second stripportions are coextensive in length.
 3. a series of L-shaped ribsinter-connecting said first and second strip portions, and
 3. a seriesof L-shaped ribs inter-connecting said first and second strip portions,and
 4. an integral blade contact carried by said second strip portionand projecting into each gap between adjacent ribs,
 4. an integral bladecontact carried by said second strip portion and projecting into eachgap between adjacent ribs,
 4. The panelboard defined in claim 1, whichfurther includes a pedestal integrally formed with one of said walls andlocated to provide mid-length support to said first strip portion. 5.The panelboard defined in claim 1, wherein said second strip portionterminates short of one end of said first strip portion, said panelboardfurther including an electrical connector mounted by said first stripportion at a location beyond the termination of said first stripportion.
 5. the spacing between adjacent ribs corresponding to the widthof a circuit breaker case, whereby said ribs act to laterally stabilizethe individual circuit breakers when installed in electrically contactedengagement with respective ones of said blade contacts; and E. commoncircuit breaker retaining means integrally formed with said backwall inparallel spaced relation to said bus bar.
 5. the spacing betweenadjacent ribs corresponding to the width of a circuit breaker case,whereby said ribs act to laterally stabilize the individual circuitbreakers when installed in electrically contacted engagement withrespective ones of said blade contacts; and E. common circuit breakerretaining means positioned in said housing in parallel spaced relationto said bus bar.
 6. The panelboard defined in claim 5, wherein saidconnector is formed having aligned slots accommodating the extensiontherethrough of the first strip portion, said panelboard furtherincluding a pedestal integrally formed with said backwall and located toprovide support for said connector.
 7. The panelboard defined in claim6, wherein said first strip portion carries an abutment for engagementwith said connector to establish its approximate position on said firststrip portion in one direction, and said pedestal is formed having meansfor engaging means carried by said connector to locate its approximateposition on said first strip portion in the opposite direction.
 8. Acircuit breaker panelboard, comprising, in combination: A. a housingincluding a backwall and upstanding sidewalls; B. a cover for saidhousing; C. a pair of spaced mounting means supported in said housing;D. a bus bar including: